Advanced RF-driven H- ion sources at the SNS

The US spallation neutron source* (SNS), will require substantially higher average and pulse H" beam current than can be produced from conventional H- ion sources such as the baseline LBNL-SNS source. H- currents of 70-100 mA with an RMS emittance of 0.20-0.35 π mm mrad and a ˜7% duty-factor will be needed for the SNS power upgrade project in 2010. We are therefore investigating several advanced ion source concepts based on RF plasma excitation. First, a generalized discussion of our source development strategy is presented as well as the performance characteristics of a large-plasma-volume, external antenna source based on an AI2O3 plasma chamber. The design and results of computational modeling of a high-power version of this source featuring an AlN plasma chamber is subsequently discussed as well as a high-efficiency extraction system necessary for high- current operation.